What is saline infusion sonohysterography (SIS)?

Saline infusion sonohysterography (SIS) or saline ultrasound uterine scan uses a small amount of saline (salt solution) inserted into the uterus (or womb) that allows the lining of the uterus (endometrium) to be clearly seen on an ultrasound scan.

“Ultrasound” is the term used for creating pictures or images using high-frequency soundwaves. The pictures are obtained using an ultrasound transducer.

Ultrasound transducers transmit high-frequency sound waves that are converted into electrical impulses that produce a moving image of the inside of the body on a screen.

Why would my doctor refer me to have this procedure?

SIS helps to see if there is any thickening or small growths (polyps) of the endometrium of the uterus that may have been seen on a prior pelvic ultrasound scan. SIS can also be carried out to assess the postmenopausal endometrium in patients who have postmenopausal bleeding.

How do I prepare for an SIS?

No special preparation is required. The scan is best done as your period finishes, day 5–9 of your menstrual cycle. So, it is best to arrange your appointment according to your period dates.

You will be asked to go to the toilet and empty your bladder before the scan. If you are using a tampon, it will need to be removed. You can still have the scan if the period is just finishing and the bleeding is light.

An SIS scan cannot be carried out if you are pregnant or if you have a pelvic inflammatory disease. You must advise your referring doctor or staff where you are having the scan if you have either of these conditions.

It is a good idea to wear comfortable clothing that gives easy access to the lower part of your body.

What happens during an SIS?

After emptying your bladder, you will be asked to undress from the waist down and you may be asked to wear a gown. You will then be asked to lie on an examination bed.

A routine pelvic and transvaginal ultrasound may be carried out before the SIS (see InsideRadiology: Transvaginal ultrasound).

A speculum (an instrument used to hold open the vagina so that it can be examined) is then inserted into the vagina. A soft catheter (a thin plastic tube) is gently inserted through the speculum and into the uterus through the cervix (the neck of the uterus).

The speculum is then removed while the catheter still remains in the uterus, and a transvaginal ultrasound transducer is inserted into the vagina.

The transducer is slightly larger than a tampon and specially shaped to fit comfortably into the vagina. A protective sterile probe cover is placed over the transducer and lubricating gel is applied to it for ease of insertion.

A small amount of saline (salt solution) is inserted through the catheter into the uterine cavity. During and after the saline injection, the transducer is then gently moved around while images of the inside of the uterus are taken.

The saline fluid within the uterus allows the lining of the uterus to be imaged clearly on the ultrasound screen and shows any endometrial abnormality.

Are there any after-effects of an SIS?

After the scan, there is a small trickle of fluid from the vagina. This is the saline fluid that was inserted through the catheter coming out. It is commonly slightly blood-stained and this may continue for 24 hours. You may wish to use a sanitary pad, but you are advised not to use tampons for the rest of the day.

Most patients feel normal after the scan with no after-effects. Some patients may have some pelvic discomfort (like mild period pain), but this settles after a few minutes up to perhaps an hour or so and is very uncommon.

A very small number of patients may have some dizziness due to the cervix being slightly irritated by the catheter. This usually passes within a few minutes and has no adverse outcome.

You will generally be well enough to drive home and resume normal activities, such as going back to work.

How long does an SIS take?

The entire procedure usually takes approximately 30 minutes. Most of this time is taken up by scanning before and after the saline is put into the uterus. The actual time taken for the saline to be put in is only 2–3 minutes.

What are the risks of an SIS?

The scan is very safe. The main risk is that of infection within your uterus being introduced by the procedure. This is extremely uncommon and is treated with antibiotics if it occurs.
Infection may present as pelvic pain that does not settle or you may develop an odorous vaginal discharge.

In this case, you should ring the clinic where your procedure was done and ask to speak to the radiologist who carried out the procedure or see your general practitioner explaining you had the procedure and describing your symptoms. Antibiotics may then be prescribed.

What are the benefits of an SIS?

Inserting the saline fluid into the uterus allows very clear ultrasound images to be taken of the lining of the uterus, and any abnormalities, such as thickening of the endometrium or polyps, can be easily seen. This will help to guide the discussion between you and your doctor about any further investigation or treatment that may be needed.